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In this paper, a new recursive linear-in-the-parameters nonlinear filter is presented. This filter is an extension of the even mirror Fourier nonlinear filter, so called because of the even symmetry of its trigonometric basis functions. The new recursive filter is used as a controller in a feedforward scheme exploited for active noise control to take into account simultaneously the nonlinearities,...
In this paper, we propose a method for repeatedly updating the coefficients of the feedback control filter used for canceling a feedback path from a loudspeaker to a noise detection microphone. The coefficients are usually estimated by feeding a sequence of extra noise to the loudspeaker. However, feeding such extra noise under active noise control is undesirable. The proposed method estimates the...
We analyze the learning curves of the FXLMS algorithm using a statistical-mechanical method. Cross-correlations between the element of a primary path and that of an adaptive filter and autocorrelations of the elements of the adaptive filter are treated as macroscopic variables. We obtain simultaneous differential equations that describe the dynamical behaviors of the macroscopic variables under the...
This paper presents analysis and design of a real time active noise control system for cancelling the acoustic noise generated by an HVAC (Heating Ventilation and Air-Conditioning) unit within a 3-dimensional enclosure. The system described in this paper is a single channel system using a feedback ANC architecture. We will test the viability of this system using both synthetic tonal noise generated...
Presence of strong broadband acoustic noise interferes with imaging process and diagnostic procedures in Magnetic Resonance Imaging rooms, especially in functional MRI (fMRI) applications. In this paper, we present active noise control (ANC) methods for reducing the acoustic noise generated by a 3-Tesla fMRI machine during the scan using Echo-Planar Imaging (EPI) technique. Properties and decomposition...
Acoustic noise problems become more and more serious with increasing use of industrial and medical equipment, appliances, and consumer electronics. Active noise control (ANC) has been studied to solve such acoustic noise problems. ANC is a technique based on the principle of superposition, i.e., an antinoise with the same amplitude and opposite phase is generated and combined with an unwanted noise,...
Magnetic resonance (MR) images are prone to inhomogeneity artefacts that hinder an efficient automatic segmentation. Existing correction methods are often dependent on initialization and computationally expensive. This paper proposes a novel variational approach for the simultaneous bias field correction and image segmentation together with its efficient implementation, which produces the global solution...
The presence of ring artifacts in X-ray computed microtomography affects the qualitative and quantitative analyses of the reconstructed images. Although digital image processing approaches to ring artifacts removal via direct filtering of the reconstructed images exist, in synchrotron radiation microtomography this issue is usually faced during the actual reconstruction process by de-striping the...
Intraocular lenses (IOLs) are widely used in cataract surgery. There is a variety of IOLs depending on lens material, optical and mechanical design. Evaluation of the visual performance obtainable with intraocular lenses is important for objective comparison between IOL models. Indeed, the visual performance of implanted lenses has a deep impact on the life of the subjects, having medical, social...
The problem of detecting cell nuclei in fluorescence images may be faced by means of a segmentation step, to get the neighbourhood of candidate nuclei, followed by a binary classification step. Important for the latter step is the choice of the descriptors (features) to be extracted from the neighbourhood and used by the classifier. In the present paper, based on a large set of manually labelled samples,...
Level-set methods have proven to be powerful and flexible for computer vision and medical imaging applications. Unfortunately, their drawback is the high computational effort required, which hampers the applicability to imaging tools for real clinical use. A new interactive 3D segmentation tool is presented, addressing operational speed issues by computing level-set surface models interactively. Real...
High-frequency percussive ventilation (HFPV) is a non-conventional mechanical ventilatory strategy which has proven useful in the treatment of a number of pathological conditions. HFPV usually involves the usage of endotracheal tubes (EET) connecting the ventilator circuit to the airway of the patient. The pressure of the air flow insufflated by HFPV must be controlled very accurately in order to...
Diabetic macular edema is characterized by hard exudates. Presence of such exudates cause vision loss in the affected areas. We present a novel approach of segmenting exudates for screening and follow-ups by building an ethnicity based statistical atlas. The chromatic distribution in such an atlas gives a good measure of probability of the pixels belonging to the healthy retinal pigments or to the...
Multifractal characteristics of the retinal vascular networks in healthy patients and patients with peripapillary atrophy (PPA) are compared in the paper. Segmented and skeletonized fundus images from the DRIVE database were analyzed over the image region corresponding to the macular area and over the whole image. The regional and overall multifractal characteristics of fundi could serve as further...
Diabetic retinopathy is one of the leading disabling chronic diseases, and one of the leading causes of preventable blindness in the world. Early diagnosis of diabetic retinopathy enables timely treatment and in order to achieve it a major effort will have to be invested into screening programs and especially into automated screening programs. For automated screening programs to work robustly a representative...
The continuous development of automatic retinal diseases diagnosis systems based on image processing has shown their potential for clinical practice. However, the accuracy of these systems is often compromised, mainly due to the intrinsic difficulty in detecting the abnormal structures and also due to deficiencies in the image acquisition which affects image quality. Light flares are one of such deficiencies...
In this paper, we provide a comparative evaluation of preprocessing methods for microaneurysm detection in color fundus images. Our aim is to achieve high sensitivity values in the candidate extraction phase. This requirement can be fulfilled if we select an appropriate preprocessing method for the candidate extractor. Our experiments showed that Contrast Limited Adaptive Histogram Equalization achieved...
In this paper a novel approach to improve exudate detection in color fundus images is proposed. Image databases usually contain images with different characteristics, thus determining an optimal parameter setting of an algorithm is a challenging task. To overcome this problem we cluster the image databases. For each cluster an optimal parameter setting is determined for the same algorithm. We extract...
The emergence of massively parallel architectures, along with the necessity of new parallel programming models, has revived the interest on dataflow programming due to its ability to express concurrency. Although dynamic dataflow programming can be considered as a flexible approach for the development of scalable applications, there are still some open problems in concern of their execution. In this...
This paper presents a dataflow design methodology and an associated co-exploration environment, focusing on the optimization of buffer sizes. The approach is applicable to dynamic dataflow designs and its performance is presented and validated by experimental results on the porting of an MPEG-4 Simple Profile decoder to the STM STHORM manycore platform. For the purpose of this work, the decoder has...
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